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Discussion Starter · #1 ·
Hello all I’m new to this forum and I need some advice regarding my situation! I’ll try to explain with as much detail as possible.. The car is a 1981 vw rabbit pickup with a turbo Diesel engine out of a mk2 Jetta. I believe the engine code is MF. So it started running hot towards the end of the season in the fall of last year. So I topped off the coolant last fall and idled it for half hour and it ran fine before I covered it up for good. Yesterday when I popped the hood the coolant was at the very base at the reservoir, but not empty. The oil was black and free of water droplets or anything like that. I started up the truck and i watched immediately the coolant level started to come up relatively fast. The truck did not smoke anything at all (and never has before) except for a minor puff of black as soon as it fired up. Other than that not really anything at all coming out the tailpipe. The hoses were soft the whole time, even when the truck had warmed up. I had the truck running for over an hour. When it warmed up one notch over center the aux fan came on only once, but after that it did not come on agian and the temp stayed past the middle, even with the heat cranked. Even when the truck was warmed up I was watching the reservoir tank and there were tiny bubbles coming up periodically. The coolant was clean the entire time with no evidence of contamination. I shut the truck off since the temp wasnt going down, and restarted it after a few minutes a few times to let the temp come down, which it did with each restart. Every time it was restarted, there were a few bubbles that would come up through the reservoir tank as soon as it was started. When I shut the truck off for good I could see the coolant level go down in the reservoir and today I popped the hood again and the coolant level was the same as it was before I started it the first time yesterday. I believe I have a bad head gasket, but how come my fluids are clean and hoses are soft? Only thing not right is the fact that bubbles appear and the truck begins to run hot soon after it has fully warmed up...
Any suggestions would be greatly appreciated, and also there are no wxternal leaks around the rad or water pump..
I apologize for the lengthy post but I wanted to explain as much as possible!
Thanks in advance
 

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Welcome Clapped Caddy,
I read through your post and was looking for a space in-between thoughts once in a while but then grammer is low on the list here. Getting the Caddy to cool down is what you want.

So this problem of running hot came on late last season. When you unwrapped the car this spring you find the reservoir down a bit and it was full last fall. Fluids don't evaporate much when in the proper container so you have a leak.

But not to the oil that you can tell, and not through the exhaust that you can tell. Allowing a diesel to start and idle will almost never get it hot enough to bump the gauge up beyond the normal range. You would have to block off the radiator or drive it to put a load on it to get it to get hot. Cranking the heat on in the cab actually is stealing heat away from the engine and delivering it to the interior of the car. Hence the name, heater.

If you have looked at this site long you will have read about placing a light rubber glove over the neck of the radiator reservoir and I have found securing it with a few rubber bands so it won't come off to be a great help. Yo do this prior to starting a cold engine. After starting the engine if the glove inflates then you know that air from the cylinders is getting pushed into the coolant system in some way.

How might that happen? HEAD GASKET FAILURE. So try that. Put a glove on it. Start and rev the engine a little bit and watch the glove between that space between the hood and the dash. I would even go as far as letting it warm a bit and then apply the e brake and play the clutch against the engine and get the boost to come up. IT is amazing the amount a few pounds of boost increases the compression ratio.

Try that and report back.
 

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Discussion Starter · #3 ·
Welcome Clapped Caddy,
I read through your post and was looking for a space in-between thoughts once in a while but then grammer is low on the list here. Getting the Caddy to cool down is what you want.

So this problem of running hot came on late last season. When you unwrapped the car this spring you find the reservoir down a bit and it was full last fall. Fluids don't evaporate much when in the proper container so you have a leak.

But not to the oil that you can tell, and not through the exhaust that you can tell. Allowing a diesel to start and idle will almost never get it hot enough to bump the gauge up beyond the normal range. You would have to block off the radiator or drive it to put a load on it to get it to get hot. Cranking the heat on in the cab actually is stealing heat away from the engine and delivering it to the interior of the car. Hence the name, heater.

If you have looked at this site long you will have read about placing a light rubber glove over the neck of the radiator reservoir and I have found securing it with a few rubber bands so it won't come off to be a great help. Yo do this prior to starting a cold engine. After starting the engine if the glove inflates then you know that air from the cylinders is getting pushed into the coolant system in some way.

How might that happen? HEAD GASKET FAILURE. So try that. Put a glove on it. Start and rev the engine a little bit and watch the glove between that space between the hood and the dash. I would even go as far as letting it warm a bit and then apply the e brake and play the clutch against the engine and get the boost to come up. IT is amazing the amount a few pounds of boost increases the compression ratio.

Try that and report back.
My apologize if my thoughts were all over the place in my original post! I was writing quickly to regurgitate as much as I could remember in detail. Anyhow, thank you for the quick reply! I have heard of that method and will try it out when the weather warms up again in a few days and report back.
 

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Yeah, just like our diesels we can tend to throw a runaway at times as well. Hope you get it figured out. I went with ARP studs and that seems to have helped me.
 

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Discussion Starter · #5 ·
Wow, almost a year has gone by since my last visit! March 12 (when I originally posted) was one of the last days of in-person classes for me. The world definitely changed significantly for us in that week especially.

Anyhow, thank you @ORCoaster for your advice with my problem, and apologize for replying after so long.

For those interested, I have since fixed my truck and was able to put on around 1500 trouble free kms on it.

The problem was indeed the head gasket. It was a bit of a headache to fix, at least for me. It turned out to be one of those tasks where it is just one small setback after another. These things included a broken screw from the coolant hose inlet flange (requiring careful drilling), dropping a washer into one of the ports, having the spare head gasket "on hand" only to realize at the last second that its wrong etc.. Doing the whole procedure outside did not help either. On the bright side, the head and block were not warped or cracked at all.

I figure that I must have had compression leaking into the coolant system due to a head gasket that was not fully sealing. This would explain the bubbles/foaming that could be seen in the reservoir. Keep in mind that the the bubbles would start after the truck had warmed up a bit, and would remain from then on. I do not have any bubbles visible in the reservoir now, and my coolant level stays consistent, unlike before. The truck now runs nice and cool. I'm not entirely sure what caused this leaking head gasket, but I hope the truck continues to treat me well in the future. Overall, it was a good learning experience in terms of trouble shooting and repair. Very rewarding as well.
 
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