88 random overheating troubleshooting and prevention with new engine (Page 1/1)
cartercarbaficionado DEC 10, 02:16 AM
so it got blown up litterally 2 weeks before i was going to pick it up but i already payed for it and had a new engine anyways to replace the one that was in it due to its lack of power and low end torque, between it making 12 psi oil pressure at a hot idle and just general poor running and being so hot it torched the stainless exhaust rainbow all the way to the tips when it overheated once i have 0 love for that engine.
i have a new unknown 86 engine since thats what was in it already and i have the correct flywheel and a new clutch for it and just need to generally regasket it and clean a few things mainly the cooling passages since i aint going through the constant fear of the car overheating for seemingly no reason.
i checked the weather every time it overheated and kept enough of a log to see there wasnt really a pattern other than speed. it overheated constantly when driven at 70 mph and during that time had a sitting temp of somewhere around 220, new water pump, bigger rad, better high flow fan and cleaning the system over and over seemed to have no effect, sometimes it would go literal months between overheating and sometimes 45 minutes, the coolant pipes arent crushed and there doesnt seem to be any flow restrictions anywhere other than it had a thermostat that wouldnt open one time but a new one solved that and was proved by removing the thermostat every single time it overheated after that. ive never had a temp gun to check the radiator but it always flowed fine and you could feel a difference in temp by hand between the input and output
ive had a long running theory that maybe at the lower rpms its cavitating and not able to flow as well as it should but ive never seen any indication of that with either rad cap removed (yes i am calling the thermostat cover a radiator cap) has anyone else experinced a 2.8l v6 overheating for seemingly no reason with everything checking out and if so did you find a fix?
and before someone chimes in....yes i cleaned the fins and cores many many times that thing so was clean i would have ate off it no questions asked and you could see through it just fine from a few feet away, yes it is a ac car but its never actually had that functonal and the condenser has been cleaned a few times as well and while it does have a large amount of red overspray its not the issue, though it could be argued as unhelpful in the first place
olejoedad DEC 10, 06:36 AM
1. The water inlet hose to the water pump is collapsing at high rpm.
Is there a spring inside the water inlet hose?

2. Rainbowing the exhaust headers can be caused by a lean condition, or perhaps jumping time.., or improper timing.
82-T/A [At Work] DEC 10, 08:02 AM

quote
Originally posted by olejoedad:

1. The water inlet hose to the water pump is collapsing at high rpm.
Is there a spring inside the water inlet hose?





I'd never considered this one!
olejoedad DEC 10, 10:00 AM

quote
Originally posted by 82-T/A [At Work]:
I'd never considered this one!



I had the same problem years ago on my 4.9 swap.
It was fine until the rom got up to interstate speeds, then it would overheat.
It took a while to suss it out, a new hose solved the problem.

[This message has been edited by olejoedad (edited 12-10-2025).]

cartercarbaficionado DEC 10, 01:00 PM

quote
Originally posted by olejoedad:

1. The water inlet hose to the water pump is collapsing at high rpm.
Is there a spring inside the water inlet hose?

2. Rainbowing the exhaust headers can be caused by a lean condition, or perhaps jumping time.., or improper timing.


it does have a spring in it since i had considered that but it doesnt overheat at high rpm which is the weird thing. it will overheat at 70 mph in 5th gear and at residental speeds but not faster or slower

timing has been verified on that old engine 23 different times, ive had the timing cover off and marked everything and still didnt trust it and replaced the chain, guide and gears and remarked it again much clearer and retimed the dist to what the emissions sticker said (I think it was 10° btdc off the top of my head) lean could be but the computer didnt think so and every sensor checked out when manually checked and a old exhaust emissions sniffer said it was a bit lean at 15-1 but thats not too bad, the headers themselves are still the stock kinda crappy looking rusty finish and the stainless is after the y-pipe as the ocelot kit which i encourage no one to buy since it fits rather poorly even after trimming
olejoedad DEC 10, 01:50 PM
Pumps don't cavitate at low rpm and then not cavitate at higher rpm, so you can toss your cavitation theory.

Do you have all of the front end ducting to the radiator in place, including the air dam below the radiator core support?
cartercarbaficionado DEC 10, 06:34 PM

quote
Originally posted by olejoedad:

Pumps don't cavitate at low rpm and then not cavitate at higher rpm, so you can toss your cavitation theory.

Do you have all of the front end ducting to the radiator in place, including the air dam below the radiator core support?


yes? its a complete aeronose front with the air dam and the metal mounting plate