The Mitsubishi 4G32 and you. A comprehensive guide to surviving poor financial decisions and overhauling a terrible engine.

[Scott Cee]

I will preface this by saying if you have the Mitsubishi 4G32 engine, and it is bad enough you need to rebuild it, you're likely better off retrofitting the machine with something else. Nobody told me that before I was already too deep into it, so I will share what I learned.

The step by step thread is available here: https://www.forum.4x4north.com/viewtopic.php?f=18&t=463 This was me muddling my way through it. I'll try to offer a more polished view here with the value of hindsight.

To start, here is the parts list that so many people ask for. You can cross these partnumbers to others, Rockauto is an excellent source for this and I have included application data where available to make this easier.

When I write "NLA" it means No Longer Available. You're going to get used to seeing that when you deal with this engine.

Parts list for Bobcat 4G32 rebuild:
Main bearings: ITM Engine Components P/N 5M1147 (5M1147-020 for 20 under) Application 1981 DODGE COLT 1.6L 98cid L4
Rod bearings: Mahle/Clevite P/N CB1120A4 (CB-1120A-.50MM(4) for 20 under) Application 1981 DODGE COLT 1.6L 98cid L4
Pistons: Safety Auto Parts P/N SP-902 (SP-902-3 for 30 over or maybe SP902.030) Application 1985 MITSUBISHI MIRAGE 1.6L 98cid L4 Turbocharged (Note, these may no longer exist, not sourced through Rockauto)
Rings: Safety Auto Parts P/N 2C675 (2C675030 for 30 over) (Note, these cross to a Hastings set that fits the N/A Colt engines, but they are what the piston manufacturer specs, they appear to just be a thicker ring than what was used originally with the Mirage)
Valve guides: P/N 1407576 and 1407577 (Note, not sure which is intake and exhaust or manufacturer)
Gasket kit: FEL-PRO P/N HS8974PT Application 1982 DODGE COLT 1.6L 98cid L4 (Note, is the top end only, but has a nice MLS headgasket)
Gasket kit: ITM Engine Components P/N 0900302 or 0900302:8 Application 1982 DODGE COLT 1.6L 98cid L4 (Note, complete set but the intake gasket is wrong, the FEL-PRO kit has this gasket or see below)
Intake manifold gasket: APEX P/N AMS2190 Application 1981 DODGE COLT 1.6L 98cid L4 (Note, didn't use this one but it looked correct)
Intake manifold gasket: ITM Engine Components P/N 0950345 or 09-50345 Application 1981 DODGE COLT 1.6L 98cid L4 (Note, this P/N is the same as a FEL-PRO gasket, but I believe it is NLA)
Timing belt: ITM Engine Components P/N 4105 Application 1989 DODGE COLT DL 1.8L 107cid L4 (Note, may also be a Mitsuboshi CD93, not confirmed)
Timing belt tensioner: BECK/ARNLEY P/N 0241090 or 0241090:8 Application 1989 DODGE COLT GT 1.6L 98cid L4 Turbocharged (Note, had P/Ns 552-294 and MD109958 written on box, SKF P/N TBT75101 may also be right)

Carb kit: WALKER PRODUCTS P/N 15581B Application 1977 DODGE COLT 1.6L 98cid L4 (Note, does not have correct needle or seat)

Plug wires: DENSO P/N 6714007 or 671-4007 Application 1982 DODGE COLT 1.6L 98cid L4
Distributor cap: STANDARD MOTOR PRODUCTS P/N JH67 or JH-67 Application 1977 DODGE COLT 1.6L 98cid L4
Distributor rotor: STANDARD MOTOR PRODUCTS P/N JR80 or JR-80 Application 1977 DODGE COLT 1.6L 98cid L4
Spark plug: Autolite P/N 66 (Note, these are what Bobcat specs but can be replaced for any similar plug or better. They are probably not worth the premium for a very old design of plug if you've upgraded to electronic ignition)
Electronic ignition upgrade: Pertronix P/N 1941
Coil: STANDARD MOTOR PRODUCTS P/N UC12

Thermostat: MOTORAD P/N 5240180 or 5240-180 Application 1977 DODGE COLT 1.6L 98cid L4
Radiator cap: STANT P/N 10228 (Note, no application specified, is a direct cross to the Bobcat P/N)
Radiator hose: Bobcat P/N 6571683
Radiator hose: Bobcat P/N 6571682
Temperature sender: Bobcat P/N 6658818 (Note, available aftermarket but pricing is similar to OEM Bobcat, for use with new style gauge P/N 6669663 only, sender P/N 6599492 for old gauge is NLA)

Belt (waterpump): Continental P/N 11AV1030 or 15411
Belt (governor): Continental P/N 11AV800 or 15321
Air filter: Bobcat P/N 6646494 or Luber-Finer LAF1275 or NAPA FIL 2276 or 2276FR
Oil filter: Bobcat P/N 6696286 or WIX 51324 or Donaldson P550935 or Hastings/Baldwin LF144 or B173-S or NAPA FIL 1381 (Note, NAPA is a direct OEM cross, the others are similar and may offer slightly different filter efficiency)

Muffler: Bobcat P/N 6514737 (Note, buy generic aftermarket, they're all over the internet)
Exhaust flex pipe: (Note, correct part is NLA, used a 6569624 generic aftermarket and cut it down to fit)

Starter: Wilson P/N 91014247 or 91-01-4247 (Note, purchased but still running starter it came with, plan to swap it out as Bendix drive is damaged)

Parts I didn't get:
Oil pump rotor: Bobcat P/N 6632733 (Note, NLA from Bobcat, might be some dead stock out there. Aftermarket part 6632733-AM was shown as existing, but no stock. Ultimately I determined my rotor was fine, gerotor pumps don't wear quickly)
Oil pump housing: Bobcat P/N 6660302 (Note, NLA from Bobcat, there is used units available but not much point in buying one unless you were to use it to attempt relining the pump housing. Dodge Colt part is different)
Water pump: Bobcat P/N 6632822 (Note, available but very expensive, decided to reuse the one I had. There is now some listings of knockoff/aftermarket ones. Purchased a Dodge Colt waterpump and it could be adapted but not easily)
Distributor: Cardone P/N 31649 or 31-649 1981 DODGE COLT 1.6L 98cid L4 (Note, this is an electronic distributor but should just be plug and play, I cleaned/repaired my existing distributor instead. Bobcat part is NLA)
Alternator: Wilson P/N 90317000 or 90-31-7000 (Note, alternator I had is fine, but would like to have a spare. This alternator is not cheap, I suspect a GM 1-wire "Delco 10SI" type could easily be adapted)

More posts to follow, when I feel like it.

 

[Scott Cee]

There isn't anything overly tricky about this engine, either from taking it apart or putting it together. It's all basic stuff. The main issue is parts.

Pulling the engine out is awkward:

To do this again as a full re and re, I would pull the radiator, muffler, and support off the top, and then cut out that center bar. This would allow you to pick the engine out (and back in) without a bunch of dragging, shoving, etc. One could just make some brackets to bolt that support back in after. If you're pulling the engine you should pull and clean the radiator and hydro cooler while you're in there anyway. Yes, you can get it in and out without doing this, but this is my comment in hindsight. The Bobcat manual literally says to hook up to the engine and drag it out, then support it while half out and rerig so you can pick it up straight. This is what I am doing in the above picture.

Squirrel fan and drive coupling viewed with the engine out:

Part of why I say adapting another engine is likely a better choice is how simple this design is for the drive assembly. The fan is what the drive coupling bolts to, and the fan just bolts to the flywheel with 6 bolts. Most flywheels could easily be turned on the lathe to accept this fan, and one would not even need to use a mill to drill/tap it for the 6 bolt pattern. Also, this was a standard pattern that Bobcat used, so a flywheel for whatever other engine you choose is possibly available from a wrecker. This is just my comment after having done all of this, yes, there is more to it.

 

[Scott Cee]

As far as disassembly went, it told the story of what likely happened to this engine, along with more things I found later.

The engine had been overheated at some point and popped the headgasket, whoever replaced it could not find the intake gasket so they RTV'd the intake on (bad). The manual calls for RTV around the coolant passage only, trust me they did the whole thing and there was no gasket. There also wasn't a thermostat in the housing when I took it apart:

Likely the heat from that had contributed to a valve guide failing, as is evident by the oil in the #3 chamber and cylinder:

The Gerotor pump, it's okay and I could not get one so it wound up being reused:

Oil pickup screen was in the process of clogging. I believe this was because the overheating event/coolant contamination caused the paint on the inside of the oil pan to fail and most of it wound up here. This may have partially starved the engine for oil, along with the damage that coolant contaminated oil does, so all main and rod bearings were in rough shape:

Long block ready to go to the machine shop. I did not take it apart any farther as they requested I bring them a long block and a dressed head:

The other causes of failure were that likely the rear main and back of the valve cover leaked oil into the squirrel fan, when then deposited it onto the hydro cooler and radiator. They then both plugged with dirt/mud/schmoo. At some point someone had removed and never reinstalled the access panel for the cooler that goes on the fan shroud, so no air was flowing through the radiator at that point. They may have got away with the headgasket failure, but continuing to run the engine like this resulted in serious deterioration. It still ran when I bought it, but barely, and it used oil faster than fuel.

 

[Scott Cee]

Inside of the oil pan with flaking paint, and then all paint removed:

This took a long time to do. There is no paint left, the colour difference is from a zinc or phosphate coating that was under the paint, in some places I wound up removing it and others I didn't. The point is you need to put the time in with this sort of thing if you're going to do a rebuild, or it will cause you problems later. If I had done this in my bead blaster it probably would have been faster, but I didn't for various reasons.

 

[Scott Cee]

This all took me months to do because we were waiting on parts and machining for so long.

So, while that was going on I "rebuilt" the carb. This carb is total hammered dogpoo. I think I should have just ordered one of the Chinese carbs and not tried to save it, but it is still on my engine right now and is working okay. The carb the machine comes with is a Mikuni Solex item that does not seem to be at all available, I found some listings for similar ones, but they all were from sketchy sources and had big shipping charges or absurd lead times.

Carb and intake:

Not really a 2 BBL, she's got a plug in the one side:

Intake will take a 2BBL carb, this pattern was used by Toyota and Suzuki, so there is stuff out there:

Carb split:

This float/needle/seat setup is unique to the Bobcat. My kit did not have the parts to fix this. I wound up lapping the needle and seat with valve grinding compound and a drill. It never wound up being perfect but it worked. The red gaskets under the seat are the shims to set float/fuel height:

Cleaned up:

Rebuild kit:

Accelerator pump housing is badly corroded from water contamination/ethanol gas. I was never able to make the accelerator pump work, the machine does run okay despite it but you can not go from idle to "full throttle" quickly or it will stumble:

Difference between the needle valve and seat in this kit. You can't use the one it comes with, they don't work with the float. There was some floats available, and some other kits are rumoured to have the right valve and seat, but I didn't try buying a ton of parts to see because the carb is realistically junk even though I got it to run decent:

 

[Scott Cee]

Carb back together:

They (being some PO at some time) managed to strip/mangle the threads for the intake elbow/hat, I wound up putting a stud in this with an epoxy that's similar to JB weld, and I have no doubt it will hold fine:

 

[Scott Cee]

Out of order but worth mentioning, here is a Bobcat waterpump beside the Dodge Colt one:

Could you make it work? Yes, but it's not anything close to bolt on. The pulley mount bolt pattern is wrong, and the overall height is wrong, so you would have to make an adapter on the lathe/mill, which certainly is doable. The outlet is wrong, you could cut it off and thread a hose barb into it, or weld one on. You also may have to clearance the housing to make it work with the timing belt/tensioner, I don't know because I didn't try. The point is that the advice of "just buy Dodge Colt parts" is not going to work all the time. Bobcat wants a fortune for these waterpumps, and there was no knock off or aftermarket ones when I was looking, so I reused it. As of writing this there is listings for knock offs, and I ordered one for science.

 

[Scott Cee]

Also worth talking about is the timing belt tensioners. I bought a LOT of tensioners to find one that fits. I think about 10 of them in the end. My assumption was that there was no way that Bobcat would have had them make one just for them, and I was right. The 89 Colt GT Turbo part wound up being right, potentially the Mirage turbo is too. The one you need is absolutely impossible to find stock for though. Bobcat will still sell you one for some absurd amount of money. I think I paid $7 Canadian ($5 US) for the one that fit in the end. Worth noting is the one for a Clark forklift does not fit, so not all the industrial engines are the same.

The common type that doesn't fit is on the left, OEM Bobcat on the right:

The tracing shows how they are different and that you can not bolt the wrong one up:

You could cut/weld/fab the wrong one to work, but I was looking to avoid that given I believed the right part was out there. It is. Good luck finding one though.

 

[Scott Cee]

The timing belt is also not special. It is used in the 89 Colt DL with the 1.8L. I believe it was also used in other Mitsubishi 4 cylinder engines, but the part number I have did not cross to anything but Colt and Mirage applications. It is a curved cog profile (newer style) versus the old trapezoidal profile.

ITM belt top, OEM Bobcat bottom:

ITM P/N:

ITM didn't make the belt, they reboxed a Mitsuboshi belt. CD93 might be their P/N. Who knows. But there is belts that fit available for about $5 right now. I will probably buy another spare as a "just in case".

 

[Scott Cee]

Onto actually putting the engine together.

Bare block back and machined:

They decked it and bored it .030" over, along with cleaning it and putting some primer on it. I flushed all the oil galleries again to verify nothing was in them, ALWAYS do that, don't assume.

Crank in, mains torqued with assembly lube on them. The caps are numbered. I verified the crank spun freely, but not with the first set of bearings I used, I hard ordered a bunch of forklift 4G32 parts and I believe they sent me 4G33 main bearings, either way they tied up the crank and I'm glad I caught it. So, yup, always check that. Also, before torquing the mains it's good to bump the crank with a soft hammer, and bump the caps, you want to make sure they're sitting nicely:

Piston comparison, they're identical as near as we could measure and tell (expect .030 over). The machine shop pressed the pins in on the rods for me, they are press fit so be careful if you're doing it yourself. They also resized the rod ends:

Piston and ring boxes:

Pistons in with rings. One thing that wasn't so nice was trying to get the oil control rings in. The machine shop didn't cut any sort of chamfer on the cylinders after they decked the block, I should have taken a stone to it. They went, but it was not pleasant:

Semi-dressed head as I got it back. They had to take a bunch off of it to get it flat. We reused the valves, they were fine. Guides and seats were changed:

Head on with cam and rockers:

I used the Fel-Pro headgasket as it was better than the other one. I also started putting the front cover, oil filter housing, and crank pulley on. Not much to say about this stuff other than sorting through gaskets and I put Permatex copper gasket dressing on all of them. The design is marginal, I torqued all the bolts for this stuff with a torque wrench and used locktite on them, some of the bolts were missing when I had taken it apart. The oil filter housing also leaked on the first start and I wound up gaunching the bolts to get it to stop, not great.

 

[Scott Cee]

A lot of the parts for this were old stock that had been sitting. Gaskets do not like to sit forever. The cork oil pan gasket I had was not in good shape, and broke when I tightened the bolts. I wound up using RTV instead, if you do this just be careful to not have it wind up in the oil pan as you don't want to clog the pump pickup.

Likewise the intake manifold gasket that fit was damaged from shipping/sitting. The bottom one fits and was split, the top one is for the turbo cars I guess and does not fit around the water passage:

Replacements:

 

[Scott Cee]

I also painted the engine slime green because why not:

I did a terrible job. No masking, just used a piece of cardboard to control overspray.

I had the engine upside down and noticed the valve cover leaking at this plug. Out of the two gasket kits I had one fit nicely, the other didn't. The book says something about RTVing the cover here, I think its a bad idea, you will need to pull the cover off to check valve clearance after the first start. Likewise, make sure you set the valve clearance a bit loose with it cold on the bench, but make sure you do set it now:

Intake on with other stuff:

I filled the engine with oil on the stand and primed it. Another note is I filled the pump with assembly oil too when I put it on, you want to make sure it goes together with enough lube in it so it will prime. I spun the pump over with my drill and used my multimeter to verify the oil pressure switch opened, and looked in the valve cover to make sure I was getting top end oiling:

 

[Scott Cee]

Stuffing it back in the machine:

Again, awkward.

I think that's enough posting for now. Read the thread in the first link if you want the full story. I will update with more later.

 

[Scott Cee]

Cam timing. It's not hard but I saw a few sources on the internet that are not right. The arrow points at the "pointer" in the first image. This pointer lines up with the divots on the crank gear to indicate that #1 is at TDC.

There's two divots on the crank gear so you can't assemble it wrong, however you can't assemble it wrong even without them. Perhaps there was a difference in how they were originally made, but mine could only go together one way. Regardless, you line those divots up with the pointer to be #1 TDC.

Then on the cam you line the divot on the cam gear with the divot in the top of the rear timing cover. The cam gear can also only go on one way, the manual makes comments about this but mine was definitely pinned so it could only be assembled correctly on the cam. If your rear timing cover is missing or damaged, you just have to know this is straight up and down, so you can figure this out with a level or plumb bob if needed.

Then you just put the belt on, spin it around once, and push the tensioner over so there's X amount (look at the manual) of play in the belt and lock the tensioner. Not hard, but the pictures in the book aren't great and when you Google this you might get some haywire answers.

My plastic lower and upper timing covers were melted, actually the upper one wasn't even with the machine, and I determined that the Colt and Mirage did not use the same covers, so I simply omitted them on installation. This means you can not use the timing mark on the crank pulley, but if you need to figure out how the crank pulley is to be indexed to the crank gear, again just move the gear so its divots are aligned with the pointer, then put the pulley on so the mark on it lines up with the zero mark on the cover. I just set my timing using a dialback timing light and shot it off the crank pulley and finger, there is no issue with seeing them and it is more than accurate enough.

 

[Scott Cee]

I also cleaned up and trimmed out part of the wiring harness when I had it apart. If you've come this far you should at least clean and inspect your harness. I wound up changing a few wires completely and replacing a bunch of the ring terminals. It goes a long way to avoiding future issues.

 

[Scott Cee]

This is how I modified the Amazon muffler and flexpipe to make them work. The issue is that the flex pipe isn't for this engine, so it's too long and has an extra bend on it. I just cut that bend off. It was still too long, so I wound up snipping away the collar at the end of the flex piece so it would fit inside the inlet of the muffler. I cut the inlet down a bit more, then put some cuts in it so the clamp could collapse it over the now stubby end of the flex pipe. Otherwise it was a complete bolt in affair.

 

[Scott Cee]

I made a cute little bracket and added a fuel shutoff valve. I was concerned about the needle valve in the carb leaking and filling the engine with fuel, this also might have happened to the prior engine and been part of what damaged the bearings:

The other thing I did to help get it to run better was switch from ported/semi-ported (I don't honestly know what you'd call it) to manifold vacuum for the vacuum advance in the distributor. This means there is a pile more timing when running at part throttle, and it will retard some from there when going to full throttle/high power. This makes way more sense than where it was pulling vacuum from before, and reading the manual it would seem like this was what actually was intended. Lots of timing at part throttle is good, the engine likes it, it burns more efficiently and cleaner. Up to you if you do this, but it really helped mine run better. I also threw about 10 degrees of base timing at it this way:

 

[Scott Cee]

Overall I'm happy with how it turned out, but to do it over I'd have bought an old reefer unit and harvested the Kubota diesel out of it, or something like that.

I may well still swap the carb out, I bought a cheap Toyota/Suzuki carb off Amazon for that. This one works pretty decently all considered, but it's still a bit of a pain to get it to start.

There is other issues I need to work out with the machine, but nothing major, and I have some parts to throw at it when the time comes. I'm also going to put some expanded metal over the vents in the rear door so sticks/rocks/fingers can't be put into the timing or accessory belts without opening the door first.

Any questions about this I will try to answer. I used the Bobcat manual and a Chilton/Haynes repair manual for some references for torques and whatnot, and if you're going to rebuild one of these please at least get the Bobcat manual and follow the basic information in it.

 

[ZekeSkyree]

Excellent walkthrough of your rebuild. Thank you so very much for sharing..... Damn glad I have the Ford motor.

 

[Dave1234]

This all took me months to do because we were waiting on parts and machining for so long.

So, while that was going on I "rebuilt" the carb. This carb is total hammered dogpoo. I think I should have just ordered one of the Chinese carbs and not tried to save it, but it is still on my engine right now and is working okay. The carb the machine comes with is a Mikuni Solex item that does not seem to be at all available, I found some listings for similar ones, but they all were from sketchy sources and had big shipping charges or absurd lead times.

Carb and intake:
View attachment 6135

Not really a 2 BBL, she's got a plug in the one side:
View attachment 6136

Intake will take a 2BBL carb, this pattern was used by Toyota and Suzuki, so there is stuff out there:
View attachment 6137

Carb split:
View attachment 6138

View attachment 6139

This float/needle/seat setup is unique to the Bobcat. My kit did not have the parts to fix this. I wound up lapping the needle and seat with valve grinding compound and a drill. It never wound up being perfect but it worked. The red gaskets under the seat are the shims to set float/fuel height:
View attachment 6140

Cleaned up:
View attachment 6141

Rebuild kit:
View attachment 6142

Accelerator pump housing is badly corroded from water contamination/ethanol gas. I was never able to make the accelerator pump work, the machine does run okay despite it but you can not go from idle to "full throttle" quickly or it will stumble:
View attachment 6143

Difference between the needle valve and seat in this kit. You can't use the one it comes with, they don't work with the float. There was some floats available, and some other kits are rumoured to have the right valve and seat, but I didn't try buying a ton of parts to see because the carb is realistically junk even though I got it to run decent:
View attachment 6144

My carb lacks the glass window to verify correct float/fuel height, and I could not find specs for setting the float with shims as you show. Do you have float height setting details you could share? thank you. This is a really great asset for all of us, whether we have to tackle it all at once, or one piece at a time.